Pipette and method



April 13, 1965 E. M. Px-:DERSEN PIPETTE AND METHOD Filed May 1. 1961 FlE 1...

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IN VEN TOR.

United States Patent O "ice lgenerally in the form of cylindrical tubes, usually glass.

In one class of pipette, the tubes are graduated. In another type, the tubes have a predetermined length and inside diameter whereby in their full state, a predetermined iixed volume of liquid is retained between the meniscuses formed at the ends of the pipette.

Pipettes of the latter type are generally formed by cutting a piece of long tubing of uniform inside diameter into sections of predetermined length to form the individual pipettes having the desired volume. It is apparent that the accuracy is dependent upon the uniformity of the inside diameter of the tubing and of the length the sections.

Pipettes made of glass are relatively fragile and must be carefully handled. In recent years, pipettes Y have been formed which are made of plastic material whereby they are flexible.

It is a general object of the present invention to provide an improved pipette.V

It is a further object of the present invention to provide an accurate pipette made of plastic material which is simple to manufacture.

It is a further object of the present invention to provide a pipette having a bore which is restricted at its ends to form capillary passages whereby it can retain .a sample by capillary action which can be simply calibrated.

These and other objects of the invention will become more clearly apparent from the following description when taken in conjunction with the accompanying drawmg.

Referring to the drawing:

FIGURE 1 shows a cross-sectional view of a pipette in accordance with the present invention;

FIGURE 2 shows a pipette of the type shown in FIGURE 1 in conjunction with a container; and

FIGURE 3 shows a pipette of the type shown in FIG- URE 1 incorporated with an automatic pipette.

Referring to FIGURE l, the pipette 11, preferably made of a thermoplastic material, has a body portion 12 of substantially uniform predetermined inside diameter and end portions 13 and 14 of reduced diameter forming capillary openings or passages 16 and 17, respectively.

The volume can be accurately adjusted by cutting the end 13 to the requisite length. A substantial error can be made in the location of the cut with only a minor error occurring in the volume. The percent error in volume due to a given error in length is dependent upon the relative volume of the body portion and the capillary portion.

A ferrule 28 is carried by the body portion 12 adjacent one end. The ferrule includes a collar portion 31 and an adjacent spaced raised portion. Together they form an annular groove 33. The ferrule may for example be formed on the body portion by injection molding.

A pipette of the foregoing character can be inserted in a vessel 61 of the type shown in FIGURE 2 which includes an opening adapted to receive a tube 62. The tube may, for example, be connected to a source of vacuum or pressure tot control the vacuum or pressure within the vessel. The chamber also includes an opening 63 having rounded edges which receives the ferrule portion 28 of the pipette. The ferrule is inserted therein and snapped into place with the rounded portion of the .'i,ll7'i,'?23 Patented Apr. 13, 1.965

opening fitting into the annular groove 33 of the ferrulc to retain the pipette and form a seal.

Operation of the apparatus is to insert thetip 13 of the pipette in a iiuid to be measured, create a vacuum in the vessel by connecting the tubing 62 to a vacuum source. As soon as a drop of fluid is observed at the other end of the pipette, it is full and retains a predetermined volume of liquid. A subsequent application of pressure to the chamber by connecting the tube 62 to a source of pressure delivers the predetermined volume of liquid'. If the vessel is made of deformable material, the increased and reduced pressure can be obtained by squeezing the vessel.

In FIGURE 3, there is shown an automatic pipette which the pipette is inserted in a dome 71 provided with an opening 72 for receiving the pipette. The dome also includes an opening 73. The dome is connected to a tube 74 which extends downwardly into a liquid 76 retained in a plastic vessel 77. Upon application of pressure to the vessel 77, the liquid will rise upwardly into the dome and submerge the end 14 of the pipette. If, subsequently, the opening 73 is closed, the liquid will be forced outwardly into the pipette to fill the same. When the pipette is full, the opening 73 can be opened, pressure released on the vessel, and the liquid will flow downwardly back into the vessel having a predetermined measured amount in the pipette. Upon a subsequent application of pressure to the vessel with the opening 73 closed,

pressure will be created in the dome 71 to deliver the measured amount of liquid.

I claim:

1. A pipette adapted to cooperate with a supporting means having .an opening to receive the same comprising `a body portion of tubular material, the ends of said body portion terminating in elongate drawn end portions each gradually converging to capillary dimension to define between said drawn end portions a measured volume, the interior surface of said body portion and said end portions forming a continuous surface between said drawn end portions, and a ferrule carried by said body portion adjacent one of said drawn end portions and disposed to support the last named end portion in cantilever style projecting through said opening so that the dr-awn end portions are free of the support, said ferrule including a collar portion and a raised portion adjacent said collar portion but spaced therefrom to form in combination with said collar portion an annular groove adapted to accommodate the material defining the opening to support the pipette from the support.

2. A pipette as in claim 1 wherein said ferrule is is molded onto a length of preformed tubular material.

References Cited by the Examiner UNITED STATES PATENTS 813,256 2/06 Takaki 73-425.6 2,097,571 11/37 Moran 73-425.6 X 2,104,325 1/38 Juda 23-292 2,237,213 4/41 Brown 73-425.6 2,311,367 2/ 43 Chambers ..-141--24 X 2,437,884 3/48 Maynard 18-47.5 2,454,194 11/48 Maynard l8-47.5 2,540,360 2/51 Ulvild 73--425.6 2,698,778 l/ 55 Guild 23-292 2,837,128 6/58 Marchant 141--24 2,974,528 3/61 Sanz 73-425.4 2,994,349 8/61 Demos.

OTHER REFERENCES Kirk: Quantitative Ultra Microanalysis, John Wiley & Sons Inc., New York, 1950 (pages 24 and 25).

RICHARD C. QUEISSER, Primary Examiner.

M. A. BRINDISI, ROBERT L. EVANS, JOSEPH P.

STRIZAK, Examiners. 

1. A PIPETTE ADAPTED TO COOPERATE WITH A SUPPORTING MEANS HAVING AN OPENING TO RECEIVE THE SAME COMPRISING A BODY PORTION OF TUBULAR MATERIAL, THE ENDS OF SAID BODY PORTION TERMINATING IN ELONGATE DRAWN END PORTIONS EACH GRADUALLY CONVERGING TO CAPILLARY DIMENSION TO DEFINE BETWEEN SAID DRAWN END PORTIONS A MEASURED VOLUME, THE INTERIOR SURFACE OF SAID BODY PORTION AND SAID END PORTIONS FORMING A CONTINUOUS SURFACE BETWEEN SAID DRAWN END PORTIONS, AND A FERRULE CARRIED BY SAID BODY PORTION ADJACENT ONE OF SAID DRAWN END PORTIONS AND DISPOSED TO SUPPORT THE LAST NAMED END PORTION IN CANTILEVER STYLE PORJECTING THROUGH SAID OPENING SO THAT THE DRAWN END PORTIONS ARE FREE OF THE SUPPORT, SAID FERRULE INCLUDING A COL,LAR PORTION AND A RAISED PORTION ADJACENT SAID COLLAR PORTION BUT SPACED THEREFROM TO FORM IN COMBINATION WITH SAID COLLAR PORTION AN ANNULAR GROOVE ADAPTED TO ACCOMMODATE THE MATERIAL DEFINING THE OPENING TO SUPPORT THE PIPETTE FROM THE SUPPORT. 